I don't really get the need for this thread, there are already threads where this has been discussed. Also based on the first two posts it seems to be for rampant speculation, not updates. Landing cradles and barge flyback of Block 5, really? You seriously think that might happen? RTLS of GTO missions? This is Block 5 of Falcon 9, not ITS.

I don't really get the need for this thread, there are already threads where this has been discussed. Also based on the first two posts it seems to be for rampant speculation, not updates. Landing cradles and barge flyback of Block 5, really? You seriously think that might happen? RTLS of GTO missions? This is Block 5 of Falcon 9, not ITS.

The topic was being brought up in other threads (e.g. the barge thread) so I gave it a place of its own.

And yes - it includes speculation, as stated in the title. We don't know, but there are opinions, so why not?

It appears it will incorporate all of the changes that both NASA and that DOD will require for their contracts

No, it will incorporate mostly the changes that Spacex requires for an efficient flight rate. NASA and DOD changes are secondary.

Secondary as in transcending block numbers but in the process of being implemented, or secondary as in a small team of design engineers will remain and continue tweaking?I am confusedó how can Block 5 not meet the spec of future customers, yet the design is being frozen and the team reassigned?

Without a tank stretch, and with the same ISP, the total impulse will be the same.

Improvements can be a result of higher thrust, or of reduced structural mass.

Isp should go up about 1% at SL with a 12% thrust increase due to higher chamber pressure. Since a substantial fraction of the booster's fuel is burned in the atmosphere, that will improve the total impulse slightly.

So whats the current speculation of reusability improvements in block 5?1. I remember something about restarting for final burn having problems because of heating from hot reentry causing bubbles and Hans commented they had a fix for that.2. Any changes to legs. Easier to remove or fold.3. ....

Logged

With ELV best efficiency was the paradigm. The new paradigm is reusable, good enough, and commonality of design.Same engines. Design once. Same vehicle. Design once. Reusable. Build once.

I think that Block 4 and 5 will enable almost all LEO missions to RTLS

Before you speculate Block 5 will bring this, please show us a single LEO mission that can't RTLS with block 4. I think you'll find that all LEO missions can RTLS without block 5.

It's actually not clear yet whether Iridium missions can RTLS, they are heavier and to a higher orbit than the current Dragon missions. (I somehow missed the "LEO" part of Ian's post.)

Per https://elvperf.ksc.nasa.gov F9 FT (block 3?) can RTLS and put 8380 kg to 625km circular @90 degrees. Iridium goes to 86.4 degrees, so that will add ~100 kg, but 10 birds and a dispenser mass 9600 kg - so no RTLS with the current version.

Will F9B5 have features that will help with BFR development (e.g. an option for cradle landing?)Will there be provisions for barge fly-back? (as per an isolated comment from Musk a while back?)

Also in-scope: FHB5

Stay tuned!

1. I doubt there will be experiments for cradle landing for F9 at all. But if there are, I see them being done with one off, highly modified rockets. I don't see them modifying their whole design and production around them.2. Same for fly back. The amount of infrastructure required on the barge is the long poll and I just don't see it being a priority.

I especially don't see them holding up Block 5 for these when they need to get in a bunch of Block 5 flights before they start carrying humans.

Will F9B5 have features that will help with BFR development (e.g. an option for cradle landing?)Will there be provisions for barge fly-back? (as per an isolated comment from Musk a while back?)

Also in-scope: FHB5

Stay tuned!

1. I doubt there will be experiments for cradle landing for F9 at all. But if there are, I see them being done with one off, highly modified rockets. I don't see them modifying their whole design and production around them.2. Same for fly back. The amount of infrastructure required on the barge is the long poll and I just don't see it being a priority.

I especially don't see them holding up Block 5 for these when they need to get in a bunch of Block 5 flights before they start carrying humans.

Before Semmel's observation, I was of the same opinion - that we might (might!) see F9 cradle landing as an isolated test towards BFR, sone on a land-based cradle, and that's that.

Semmel made a good connection in that barge fly-back, which presented so many difficulties when thought through, would become a lot easier if there was cradle landing there.

But cradle landing on a barge is even more difficult, for a number of reasons.

The priority for B5 is without a doubt to a) stabilize a working revision, b) streamline the reusability process, c) increase performance (maybe). "Trying something new" is not on the list.

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That said, B5 can follow the F9 1.1 model. Remember the big argument of whether F9 1.1 would have reusability hardware in it?

What happened was that when it was rolled out, the avionics was ready, the design was there, but legs and grid fins were only added a few flights later.

I can't rule out that legless/cradle flights are "designed in", but that the bottom-side thrusters are not even designed yet, just anticipated in the design.

No, it can't. Because hardware added after Block 5 would negate the certification. They are not going to scar vehicle for future mods. That is the whole point of Block 5. They will be done with development on Falcon 9 and only other future mods will be to fix problems and not to add a capability.

...Will F9B5 have features that will help with BFR development (e.g. an option for cradle landing?)...

1. I doubt there will be experiments for cradle landing for F9 at all. But if there are, I see them being done with one off, highly modified rockets. I don't see them modifying their whole design and production around them....

...That said, B5 can follow the F9 1.1 model. Remember the big argument of whether F9 1.1 would have reusability hardware in it?

What happened was that when it was rolled out, the avionics was ready, the design was there, but legs and grid fins were only added a few flights later.

I can't rule out that legless/cradle flights are "designed in", but that the bottom-side thrusters are not even designed yet, just anticipated in the design.

I get your point re: F9 1.1 and SpaceX iterative approach.

Room for the thrusters in the design is actually a prime example of what I don't think will be in B5. I believe they are now maximizing for robust performance based on all the lessons learned. Leaving room to install thrusters that are not yet designed strikes me as unlikely.

They'd either have to "get it right" upfront as to the location and space requirements for the thruster (and therefore already have at least a rough design.) Or they would have to keep tweaking the design for the lessons learned modifications.

I could be wrong. SpaceX always surprises me, but I guess I'm drinking the "B5 is the final F9 Kool-Aid." To be clear, I am not saying that B5 will be the final F9 design. Just that I believe the story that SpaceX wants B5 to be the final design.

Anyway, I think that's all I've got on the topic and it's based entirely on headcanon.